1. Field of the Invention
The present invention relates generally to turret punch presses having a pair of upper and lower turrets on which a plurality of pairs of upper and lower punching tools can be mounted to punch a variety of holes in sheet materials such as sheet metals. More particularly, the present invention relates to apparatus for synchronously indexing or rotating the upper and lower punching tools in the upper and lower punching turrets in such turret punch presses to make the best use of the punching tools.
2. Description of the Prior Art
As is well known, a turret punch press comprises a vertically movable ram and a pair of rotatable upper and lower turrets for holding a plurality of upper and lower punching tools which are varied in size and shape to punch a variety of holes in sheet materials such as sheet metals. The upper and lower turrets are substantially vertically spaced from each other beneath the ram. The turrets are horizontally disposed on their respective shafts which are vertically disposed so as to coaxially align with each other. Each of the upper punching tools on the upper turret is so located as to vertically align with either of the lower punching tools on the lower turret to cooperate with each other to punch holes of a particular shape. Also, the upper and lower turrets are so arranged as to be simultaneously power rotated to bring a desired pair of the upper and lower tools into position just beneath the ram so as to enable them to be worked by the ram to punch holes of a desired shape. In this arrangement, a workpiece, such as a sheet metal to be punched, is horizontally fed by a plurality (usually a pair) of clamping means into position between the upper and lower turrets. The punching is accomplished by the upper and lower punching tools which have been placed just beneath the ram by the upper and lower turrets. The clamping means are so arranged as to grip an end of the workpiece and be moved by power along both the X and Y axes in all directions toward and away from the upper and lower turrets. This brings any portion of the workpiece into position beneath the ram. Also, in order to automatically and continuously punch a number of holes which vary in size and shape in the workpiece, the upper and lower turrets and the clamping means are so arranged as to be rotated and moved under a preprogrammed numerical control.
During punching operations in the turret punch presses as described above, it is very often desired to punch a plurality of holes which are all the same in shape and size but which are different in direction in the worksheets. For example, there are instances where it is desired to punch many holes in a workpiece of T-shape and inverted T-shape. These are quite identical in shape and size and differ only in direction. As another example, it is often necessary to punch many I-shaped holes, identical in shape and size, but at different angles to an edge of the workpiece, in order to punch a radial shape in the workpiece. Of course, there are cases where it is desired to punch holes of identical shape and size in one direction in some workpieces and in different directions in other workpieces.
In conventional turret punch presses, however, it has been impossible to satisfactorily punch holes identical in shape and size but in different directions in workpieces in an economical manner. For instance, in order to punch holes in different directions in workpieces, a desired pair of the upper and lower punching tools of a desired shape and size are manually adjusted in direction in the upper and lower turrets in a conventional turret punch press. As a matter of course, however, it is very difficult and time-consuming to accurately align the upper and lower punching tools in a desired direction in the upper and lower turrets in this manner. Therefore, for the purpose of easy alignment, each of the upper and lower punching tools is provided with an alignment key. Each of the upper and lower turrets is also configured with a plurality of grooves with which the alignment key is selectively engaged in some of these conventional turret punch presses. In this manner, however, it is of course impossible to steplessly adjust the direction of the upper and lower punching tools in the upper and lower turrets to punch holes common in shape and size in all directions in workpieces. Also, it is still time-consuming and troublesome to manually change the direction of the upper and lower punching tools in the upper and lower turrets. Furthermore, the arrangement is costly and requires a plurality of grooves in the upper and lower turrets. However, the great disadvantage of the prior art devices is that it is impossible to continuously punch holes which are identical in shape and size and different in direction without discontinuing the punching operation in the configurations in which the upper and lower punching tools have to be manually changed in direction in the upper and lower turrets. In order to punch holes different in direction in workpieces in this manner, it is necessary to discontinue the punching operation to change the upper and lower punching tools in direction after having punched holes common in direction. For the above described reasons, it has often been the case that many pairs of upper and lower punching tools which are the same shape and size are mounted together on the upper and lower turrets to continuously punch a variety of holes, including those which have a common shape and size and are different only in direction. In such a case, however, the cost for the upper and lower tools is inevitably high. Also, only a limited number of pairs of the upper and lower punching tools can be mounted on the upper and lower turrets.